Interactive systems functioning in response to the actions of a user have been developed, such as video shooting games. In such shooting games, a user holds a pointing device (such as a rifle-like pointer) provided by the interactive system, and interacts (e.g., to move and shoot) with the plot displayed on a screen. The interactive system displays corresponding scenes, e.g., enemies shot, house explosion, etc. in response to the movement and other actions of the pointing device.
Although such interactive games provide great fun to users, they can not present true feeling “in the field” because they can only detect 2-dimensional (2D) movements of the hand-held pointing device; the “depth” dimension, i.e., movements in the forward and backward direction, can not be detected.
To improve this, U.S. Pat. No. 6,795,068 discloses a method which can decide the 3 D status of an object according to its 2D information. As shown in FIGS. 1A and 1B, the cited patent uses a physical object (such as a baseball bat) having strong contrast of colors. The object includes two parts 301 and 303 of different colors, for better identifying corresponding images. FIG. 1B shows the 2D image 305 captured by a camera or an image sensor, in which the 2D image 307 corresponds to the upper part 301 of the object. In the 2D image, all the information in the x-y coordinates are known; the information in the z coordinate is obtained by the ratio between the upper width w2 and the lower width w1, which determines the angle Φ. Because the object is allowed to move in every possible position in the real 3D space, its corresponding 2D image may vary in various ways; thus, to be precise, the positions to measure the width w2 and the width w1 can not be arbitrarily selected. According to the patent, it makes equidistant measurements of widths between the upper and lower ends of the objects, and averages them.
This cited patent has been commercialized successfully, but it has the following drawbacks. First, for the system to recognize the object, the shape of the object must be predefined; the user can not arbitrarily use any object. Second, the color contrast is critical for accurately capturing an image of the object; if the borderline between two parts of different colors is shielded for any reason, such by a hand or a part of the user's body, the resulted 3D information calculation may be incorrect. Third, the system needs to continuously calculate multiple widths, greatly increasing the loading of the processor in the system.
In view of the foregoing, the present invention proposes a different approach to generate 3D stereo information without the above-mentioned drawbacks. The term “to generate 3D stereo information” as used in the context of the present invention is not limited to generating a 3D image on a screen corresponding to the 3D information; it includes, e.g., presenting a corresponding response to the 3D information, such as presenting the flying path of a baseball affected by the swinging strength of a baseball bat, etc.